Parts Washers: Aqueous-Based Vs

Pacific Northwest Pollution Prevention Resource Center Practical Solutions for Economic and Environmental Vitality.

Parts Washers: Aqueous-Based vs. Solvent-Based

Introduction  Chlorinated solvents can contaminate used oil, resulting in costly disposal; Parts washers are commonly used in auto repair  Petroleum and chlorinated solvents contain shops to clean parts or components. Parts washers chemicals that may be toxic if inhaled, and include cold cleaning units, vapor degreasers and some solvents may increase the risk of cancer; conveyorized degreasers. Cleaning solutions used  Petroleum solvents evaporate quickly, making in parts washers include: 1) solvents, and 2) aque- worker exposure difficult to control; ous cleaners.  Solvent cleaning units are often the largest source of a facility’s hazardous waste; and Solvent Cleaners. Solvents clean by dissolving  Some solvents leave an oily residue, requiring away dirt. Solvents include petroleum-based sol- additional cleaning prior to painting or finish- vents such as mineral spirits, stoddard solvent, ing. and petroleum naptha, and organic solvents such  Petroleum solvents are highly flammable. as trichloroethane, trichlorethylene, benzene, and xylenes. Mineral spirits are classified as VOCs that contrib- ute to photochemical smog. The solvents also con- Aqueous Cleaners: Aqueous cleaners are pH- tain toxic components like benzene, toluene and neutral or alkaline water-based solutions that xylene. Benzene is an established human carcino- break down and remove dirt from part surfaces. gen; toluene causes central nervous system dam- Semi-aqueous solutions that contain small age; and xylene causes birth defects. The low vapor amounts of solvents are also available. pressure blend contains a chemical called n-methyl pyrrolidone which is a reproductive and develop- What’s Wrong With mental toxin. These solvents pose a toxic risk to Petroleum Solvents? workers and the surrounding community. If the solvents are improperly handled, they can contaminate the site. A solvent style parts washer is filled with several gallons of solvent that is stored in a settling pan at the bottom of the washer. A small flame-tight elec- Why Use Aqueous-Based Cleaners? tric liquid pump is immersed in the solvent and Water-based cleaners and operation systems are a skims clean solvent from near the top of the set- viable alternative to mineral spirits used in repair tling tank, and pumps it at low pressure through a and maintenance parts cleaning operations. An stiff flexible nozzle onto a metal grating above the aqueous-based parts washer is much like a large liquid where the metal components rest. Dirt and dish washer. It uses water and detergent combined dissolved heavy greases fall into the bottom and with heat and mechanical energy to provide the settle to the bottom of the tank. cleaning action.

Mineral spirits and other chlorinated solvents are Aqueous cleaning products are water-based solu- commonly used for parts cleaning because of their tions that, unlike petroleum solvents, are non- effectiveness in removing oil, grease, grime, and flammable and non-hazardous. Instead of dissolv- burnt-on carbon. However, their continued use ing grease, aqueous parts washer units utilize heat, raises significant environmental, health, and eco- pressurized water, soap action, and agitation to nomic concerns: break up dirt and grease.

This product was funded through a grant from the Washington State Department of Ecology. While these materials were reviewed for grant consistency, this does not necessarily constitute endorsement by Ecology.

Although they clean differently, aqueous cleaners ports the growth of microbes which are introduced perform as well as solvents in most cases. Some either directly into the cleaning formulation or in a units are even fully automated, thereby reducing filter. Because there are microbes, the formulation labor costs and increasing productivity. is of neutral pH. The microbes biodegrade the oil. An advantage of this system is that the bath cleans

itself and may last indefinitely without requiring Advantages of Using Aqueous-Based Solvents changeout. The majority of debris, oil, grease, and dirt should be removed prior to placement in  Lower hazardous waste generation and man- cleaning unit. Heavily soiled parts may overload agement costs; the system.  Little or no solvent vapors or aerosol mists that

can be harmful to your workers' health; Advantages Disadvantages  Equal or better cleaning performance; -Ideal for light-duty cleaning -Microbial units require more  Reduction in cleaning labor with some aqueous activities maintenance to keep microbes alive cleaning units; -Lower initial start-up costs -Difficult to clean heavy or stub-  Large cleaning capacities; -No toxic vapors, less irritating born soils to skin -Not suitable for large parts  Elimination of fire hazards; -Minimal waste production  Longer solution life.

Cleaning Systems Immersion Parts Washer There are five major cleaning system types com- This type of unit consists of a sink with a false bot- monly used today: tom. The bottom can be removed or opened so the Sink-On-A-Drum parts can soak in the reservoir. Like the sink-on-a- This type is the most common used in auto repair drum, there is a faucet and flow brush for hand de- shops. It is a sink with a brush mounted on a drum tailing the parts. The units are heated to about which contains the water-based cleaner. The sink 105°F and can contain filters and oil skimmers. has a faucet and flow brush for cleaning the parts. Both metal and plastic units are available. The water-based cleaner is heated to about 105°F. Many units have filters for removing particulates Advantages Disadvantages and oil; some units have oil skimmers. The units -Reduces scrubbing time and -More expensive than Sink-On-A- are made of metal or plastic. Because the workers’ reduces labor costs Drum units. hands contact the cleaner, the formulations used -Allows for extended soaking -May be difficult to clean with a sink-on-a-drum must have a neutral pH to prevent skin damage.

Advantages Disadvantages Spray Cabinet

-Ideal for light-duty cleaning -Difficult to clean heavy or stub- In this type of system, the parts are placed inside a activities born soils cabinet and the door is closed. High pressure spray -Lower initial start-up costs -Not suitable for large parts from nozzles flushes the parts and cleans them just -No toxic vapors, less irritating like a dishwasher. This is a more aggressive clean- to skin ing method than the other -Minimal waste production systems. The formulation can be neutral or alkaline since the workers’ hands do not contact it. The formulation is generally heated to between 120° and Enzyme Cleaning System 180°F. These units are made of metal and often These systems are generally modified sink-on-a- have filters or oil skimmers. Spray cabinets, be- drum units. They are made of plastic and the clean- cause they are automated, reduce labor costs for er is heated to about 105 degrees F. The system cleaning. (NOTE: never use mineral spirits in a includes an enzyme cleaning formulation that sup- spray cabinet as this could create a fire/explosive hazard.) This product was funded through a grant from the Washington State Department of Ecology. While these materials were reviewed for grant consistency, this does not necessarily constitute endorsement by Ecology.

Advantages Disadvantages Managing Your Aqueous --High level of cleaning perfor- --Moderate to high initial mance start-up cost Cleaning Wastes --Ideal for heavily soiled parts --Uses more electricity than Aqueous wastes are typically less toxic than petro- solvent unit --Large cleaning capacities avail- leum solvents and, therefore, managing those able --May require rust preven- wastes is often easier and less expensive. Proper tion for steel parts (rust --Automatic units reduce labor management of aqueous wastes depends on the inhibitors, additional dry- type of cleaning solution used, type of equipment, costs ing) --Lower waste management and the type of wastewater treatment system in costs the facility. (Note: It is illegal to dispose of any parts washer solutions into drywells, onsite septic systems, storm drains, or onto the ground).  Onsite Septic Tanks: No type of industrial waste Ultrasonic System may ever be disposed into on-site septic systems. This may contaminate your septic tank or drain This type of system relies on sound energy to ac- field, which may result in a costly system failure. complish cleaning. Through a process called cavita-  Oil/Water Separators: Since parts washers tion, the energy causes bubbles to form; these bub- emulsify oils and greases, disposal of aqueous solu- bles explode in crevices and holes to clean the tion into an oil/water separator is not effective. parts. These systems are most appropriate for When emulsified, oils are not separated and will cleaning complex parts like transmissions and car- simply pass through the system. buretors. Higher pH cleaners can be used in these  Municipal Sewer System: In some cases, aqueous units since workers’ hands do not contact the solutions may disposed into the municipal sewer cleaner. Like the spray cabinet, these systems are system. However, special permission is required automated so they reduce labor costs for cleaning. from the sewer utility, who may also require labora- Similarly, you should avoid using mineral spirits in tory testing of the waste. Always contact your mu- this kind of system. nicipal wastewater utility before utilizing this disposal method.  Evaporation of Aqueous Solutions: Since most aqueous solutions do not contain volatile organic compounds (VOCs) , they may be evaporated, leav- Advantages Disadvantages ing only a smaller amount of sludge for disposal. -Ideal for hard to clean parts - High initial start-up cost Some parts washers may contain special evaporator with blind holes or hidden sur- units for this specific purpose. (Note: It is unlawful faces (transmissions, carbure- to evaporate petroleum solvents for disposal purpos- tors) es). -Very high performance cleaning  Disposal by Hazardous Waste Vendor: Utilizing a -Significant reduction in cleaning waste disposal vendor is the preferred method for labor managing aqueous solutions. Since aqueous solutions are less toxic than petroleum solvents, disposal costs are generally less. Studies have shown that large waste vendors typically charge approximately 1/3 less for aqueous solutions. Furthermore, utilizing a licensed vendor reduces your liability and en- sures that the waste is properly disposed.  Disposal of Aqueous Sludge: Tests have shown that aqueous sludge typically contains toxic heavy metals and solvents and therefore, should not be disposed into the normal trash. It is recommended that all sludge be managed as hazardous waste.  Other Types of Waste: Waste such as skimmed oil sludge and solution filters should be managed as dangerous waste. (Note: The Washington Depart- ment of Ecology does not allow skimmed oil or sludge to be mixed with used oil).

Good Management Tips For a Parts time to parts cleaning, a spray cabinet would help reduce the labor cost. If you clean many transmis- Washing System sions or carburetors, an ultrasonic cleaning unit may be your best bet. Spray cabinets and ultrason-  Use the least hazardous cleaning solution in ic systems are aggressive cleaning systems, and are your parts washer; best for medium– to large-sized shops where  Check the Safety Data Sheet (SDS) before you workers have to devote a significant amount of purchase a product to ensure the least toxic time to cleaning parts with medium to heavy con- material. Use aqueous cleaners instead of sol- tamination. vents. Q3: Where can I find out about the cleaning sys-  Use a non-ignitable parts washer cleaner tems that are available? (flashpoint greater than 140°F). A: Check the Yellow Pages under the automo-  Avoid using listed hazardous solvents and pre- bile parts and supplies. Some vendors supply vent contamination of your cleaning solution equipment, other vendors supply cleaning formula- with listed hazardous solvents by avoiding the tions and still others provide waste hauling ser- use of aerosol spray cans near your parts wash- vices. er. Q4: I just cleaned a part using only hot water,  Reduce wastes by maximizing your solution without cleaning solution. Can I dispose of the life wastewater into my septic system?  Only wash parts when necessary. A: No. the wastewater may now be contaminat- ed with oils, solvents, or heavy metals. No type of  Only change your cleaning solution when it no industrial wastewater may ever be disposed into longer adequately cleans parts. Do not change on-site septic systems. your solution on a scheduled basis and only allow contract pickups when necessary. Q5: What kind of aqueous cleaner should I use?  Drain your parts thoroughly over the parts Neutral pH cleaners should be used in equipment washer to reduce loss of cleaning solution. (like a sink-on-a-drum, enzyme or immersion unit) When using aqueous cleaning units, select where workers’ hands contact the cleaner. Higher cleaning units with filtration and oil skimming pH alkaline cleaners should be used only in equip- to remove solids and oil from aqueous cleaning ment (like spray cabinets and ultrasonic leaning solutions and extend solution life. units) where there is no hand contact. The safest cleaners are those with no solvent alternatives.

Q6: If my aqueous solution and sludge is con- Frequently Asked Questions taminated by toxic metals, oils, or other solvents, how do I determine if my aqueous waste Q1: Are aqueous-based cleaners more expen- is a regulated dangerous waste? sive than mineral spirits cleaners? A: A laboratory can analyze a sample of your A: Companies can reduce labor costs by utiliz- waste to determine if it is non-hazardous or a regu- ing automatic aqueous parts washers. Start-up lated waste. This may be worthwhile for larger vol- costs may be greater initially, but many units can umes of waste, since it could reduce disposal costs. pay for themselves with increased productivity. However, for smaller volumes of waste such as Water-based cleaners are often less expensive than sludge and filters, it may be less expensive to just mineral spirits systems because they do not re- assume that it’s hazardous and dispose of it ac- quire change-out as often. Filters and oil skimmers cordingly. It all depends on the volume of waste, can extend the bath life of the cleaners. your vendor’s disposal rates, type of cleaners, and Q2: What is the best system for my shop? the individual cleaning processes. Your hazardous waste vendor can help you make this decision. A: If your shop is small with only one mineral spirits parts cleaner, and your workers devote a small amount of time to cleaning and you have light contamination, a sink-on-a-drum or enzyme system will be your best option. Enzyme systems minimize waste generation but they are suitable for only light or medium contamination. If you have multiple parts cleaners and devote a lot of